DE102010029935B4 - Method and device for supplying fuel in an internal combustion engine - Google Patents

Abstract

Method for feeding fuel into a combustion chamber of a cylinder (3) of an internal combustion engine (2), the cylinder (3) having an air-fuel mixture via at least two inlet sections (8), each connected to the cylinder via an inlet valve (9). (3). ) is injected.

Description

technical field

The invention relates to internal combustion engines in which fuel is injected into an intake manifold using two injectors. In particular, the invention relates to a control method for injecting fuel using two injectors in an internal combustion engine.

State of the art

So far, internal combustion engines have been known in which two injection valves are provided for each cylinder in an intake manifold. Eight injection valves can be provided in such a four-cylinder spark-ignition engine. The two injectors, each assigned to one cylinder, inject fuel into a region of a branch in the intake manifold in order to admit an air-fuel mixture formed there into the relevant cylinder through two separate intake valves. In internal combustion engines with two intake valves per cylinder, this has the advantage that, in comparison to internal combustion engines with only one injection valve per cylinder, less fuel is directed onto a web at the junction of the intake manifold and is deposited there. The amount of fuel deposited can only be determined with great effort, so that metering the exact amount of fuel admitted into the cylinder is difficult.

An essential aspect in the design of an injection system for an internal combustion engine is that the most homogeneous possible air-fuel mixture is present in the cylinder of the internal combustion engine at the time of ignition.

In conventional internal combustion engines, this air/fuel mixture is generated in the area in front of the intake valves. The fuel spray injected by the injectors into the corresponding intake manifold area evaporates there and is sucked into the relevant cylinder at the time of intake by a corresponding piston movement. For this purpose, the fuel is usually injected into the corresponding section of the intake manifold beforehand, so that a certain amount of time is available for the fuel droplets to evaporate in the fuel spray. This is particularly necessary in the operating ranges with higher loads.

It is the object of the present invention to provide a method and a device for supplying fuel to a cylinder of an internal combustion engine, in which better mixing of the air-fuel mixture in the cylinder can be achieved.

From the disclosure document U.S. 2009/0 241 905 A1 discloses an injection method in which fuel is injected into branches of a branched intake pipe by means of an injection valve. For each intake stroke, one injection valve injects once in front of the associated closed intake valve and the other injection valve once through the associated open intake valve. In one variant, one injection valve injects once again in front of the associated closed intake valve and the other injection valve during a single injection process both in front of the intake valve that is still closed and in the course through the associated open intake valve.

From the disclosure document JP 2009 - 185 741 A an injection method is known, according to which fuel is also injected into branches of a branched intake pipe by means of an injection valve. For each intake stroke, the injectors injected once through the open intake valves or alternately only one of the injectors injected once through the associated open intake valve.

From the disclosure document JP 2010 - 121 617 A injections from one valve before and from the other valve after the start of the intake phase are known. Further injections begin before the intake phase and overlap with the start of it.

Disclosure of Invention

This object is achieved by the method for supplying fuel to a combustion chamber of a cylinder of an internal combustion engine according to claim 1 and by the device and the engine system according to the independent claims.

Further advantageous developments are specified in the dependent claims.

According to a first aspect, there is provided a method for supplying fuel to a combustion chamber of a cylinder of an internal combustion engine, wherein an air-fuel mixture is supplied to the cylinder via at least two intake sections, each of which is connected to the cylinder via an intake valve, each an injection valve is assigned to the inlet sections, fuel being injected at least temporarily asynchronously into the inlet sections by the injection valves during an intake stroke of the internal combustion engine.

One idea of the above method is that, in an internal combustion engine in which the fuel is injected into the intake manifold by two separately controllable injection valves, carry out the injection in such a way that the vaporization of the fuel spray takes place at least partially in the cylinders. In order to avoid the disadvantages that usually arise from this, namely an inhomogeneous distribution of the air-fuel mixture in the cylinder or incomplete evaporation of the fuel spray at the point of ignition, the injectors are controlled asynchronously to one another, so that better swirling of the fuel in the Cylinders or in the intake manifold and thus a better mixing of the air-fuel mixture is achieved. This results, among other things, in an improved vapor rate in the fresh mixture.

In particular, fuel can be injected into the inlet sections alternately.

Another advantage of this operating mode is that the internal combustion engine can be operated in a partial load range with an increased exhaust gas recirculation rate (EGR rate), which in turn reduces fuel consumption.

According to one embodiment, fuel can be injected into the inlet sections by an injection valve for a period of time, the period of time having a duration that corresponds to between 2% and 30% of the duration of the injection phase of the inlet valves.

According to a further aspect, a device for controlling a supply of fuel into a combustion chamber of a cylinder of an internal combustion engine is provided, an air-fuel mixture being supplied to the cylinder via at least two inlet sections which are each connected to the cylinder via an inlet valve. an injection valve being associated with each of the inlet sections. The device is designed to control the injectors in such a way that during an intake stroke of the internal combustion engine, fuel is injected at least temporarily asynchronously through the injectors into the inlet sections.

According to a further aspect, an engine system with an internal combustion engine and with the above device is provided.

According to a further aspect, a computer program product is provided which contains a program code which, when it is executed on a data processing unit, carries out the above method.

character list

• 1 zeigt eine schematische Darstellung eines Motorsystems mit einem Verbrennungsmotor, dem Kraftstoff durch eine Saugrohreinspritzung mit zwei Einspritzventilen pro Zylinder zugeführt wird; und
• 2 zeigt einen Vergleich der Kraftstoffeinspritzung beim Stand der Technik und gemäß einer Ausführungsform des Verfahrens zum Zuführen von Kraftstoff.

Preferred embodiments are explained in more detail below with reference to the accompanying drawings.

• 1 shows a schematic representation of an engine system with an internal combustion engine, the fuel is supplied by a manifold injection with two injectors per cylinder; and
• 2 12 shows a comparison of fuel injection in the prior art and according to an embodiment of the method for supplying fuel.

Description of Embodiments

In 1 an engine system 1 with an internal combustion engine 2 is shown. In the exemplary embodiment described, the internal combustion engine 2 is an Otto engine, but it can include other types of internal combustion engines 2 . The internal combustion engine 2 has four cylinders 3 in the exemplary embodiment shown. The number of cylinders 3 is not limited to four, but any other number of cylinders 3 in the internal combustion engine 2 can be provided.

A combustion cycle, an exhaust gas discharge cycle, an intake cycle and a compression cycle are carried out in the cylinders 3 in a known manner in accordance with a four-cycle operation.

Fresh air is supplied to the cylinders 3 via an air supply system 4 . A throttle flap 5 is arranged in the air supply system 4 in order to set the quantity of air supplied in accordance with a predetermined control. The area between the throttle valve 5 and the cylinders 3 is called the intake manifold. The air supply system 4 branches in a region 6 of the intake manifold downstream of the throttle valve 5 to the plurality of cylinders 3. In the present exemplary embodiment, the air supply system 4 branches into four supply sections 7. Before the intake of the air supplied to the cylinders 3 via the air supply sections 7, the air branches the air supply section 7 into two inlet sections 8, which end at the respective cylinder 3. The air supplied through the intake sections 8 is admitted into the cylinder 3 in question at suitable intake time windows with the aid of intake valves 9 arranged on the cylinder 3 in question.

Injection valves 10 are provided immediately before the branching of the air supply section 7 into the inlet sections 8 . The injectors 10 are arranged relative to the inlet sections 8 in such a way that the spray cone of the fuel spray injected by them extends as far as possible into the respective inlet section 8 when fuel is injected, so that the smallest possible amount of fuel accumulates at a web 11 at the branching point of the feed section 7 can accumulate.

The air/fuel mixture, which has been admitted into the cylinders 3 via the intake valves 9, is ignited with the aid of an ignition device 12 at an ignition point specified according to the activation. The combustion triggered in this way causes an expansion of the combustion chamber through a corresponding movement of a piston (not shown) arranged in the cylinders 3 and thus causes a drive torque of the internal combustion engine 2.

In the subsequent exhaust gas exhaust stroke, the combustion chamber of the relevant cylinder 3 is reduced again by the piston performing a compression movement. During this exhaust gas expulsion movement, one or more (in the present case two) exhaust valves 15 are opened, as a result of which the combustion exhaust gases present in the cylinder 3 are expelled into an exhaust gas discharge section 16 . The combustion exhaust gases are then discharged into the environment via any catalytic converter (not shown).

The engine system 1 is operated with the aid of a control device 20, according to a specification V, which can correspond, for example, to a drive torque to be provided. For example, this specification can correspond to a driver's desired torque if the engine system 1 is an engine system of a motor vehicle. Control unit 20 is actuated by adjusting actuators, such as the throttle valve actuator for adjusting throttle valve 5, injectors 10, with an injection point and the injection duration being specified, the ignition device for igniting ignition device 12, with the ignition point being specified, and other actuators.

The control takes place as a function of specification V and of state variables of engine system 1, which can be detected by appropriate sensors and/or modeled from other state variables and/or their dynamic behavior. Such state variables can be, for example, the intake manifold pressure in the intake manifold, the speed of the internal combustion engine 2, the load on the internal combustion engine 2, the exhaust gas temperature and other state variables.

In a conventional control of an internal combustion engine with such a configuration, i.e. with two injectors in an intake manifold branched into two inlet sections, the injection is usually carried out earlier in time. That is, before the intake valves 9 take in the air-fuel mixture into the cylinders 3, fuel is injected into the intake portions 8 .

A representation of such an injection is in the upper part of the 2 shown. The time curves of the valve lifts ENW of the intake valves and the valve lifts ANW of the exhaust valves are shown there. Control signals EA1, EA2 for the injectors in the case of an upstream injection according to the prior art are shown below in relation to this in terms of time. Control signals EA1, EA2 for the injection valves in an injection according to the method proposed here are shown at the bottom.

In the method according to the prior art, before the intake valves 9 open, the two injectors 10 assigned to a cylinder 3 are actuated simultaneously. As a result, the entire quantity of fuel is injected into the intake manifold or into the inlet sections 8 before the inlet valves 9 are opened. In this way, almost all of the fuel can already evaporate in the inlet section 8 before the inlet valves 9 open, and the finished air-fuel mixture can thus be admitted into the cylinder 3 .

Improved operation is also obtained, for example, if injectors 10 are asynchronously actuated in accordance with the illustration below of the actuation signals of injectors 10 . When the fuel flows into the combustion chamber, inhomogeneities arise in the distribution of the air-fuel mixture, which can lead to irregular combustion with worsened emission values. In order to achieve even better turbulence of the fuel spray in the combustion chamber, it is now provided that fuel spray is injected at different times through the injectors 10 assigned to a respective cylinder 3 .

This asynchronous activation can take place before and/or during the phase during which the intake valves 9 are open. This creates a turbulence. At least part of the fuel spray reaches the combustion chamber of the relevant cylinder 3 and only evaporates there, as a result of which the combustion chamber is cooled overall. As a result, the knocking tendency of the internal combustion engine 2 can be significantly reduced, particularly at full load.

According to one embodiment, as in 2 shown the injection take place alternately. In this case, starting with a first of the injectors 10, fuel is injected for a first injection period t1. After the first injection duration t1 has elapsed, the injection of fuel through the first injection valve 10 is terminated and fuel is injected for a second time duration t2 through a second of the injection valves 10 . After the end of the second period of time t2, injection is carried out again with the first injection valve 10 and the process is repeated. This alternative fuel zen can be carried out during the entire phase during which the injection of fuel is to take place. The first and second durations t1, t2 can have the same duration or different durations. The first and second durations t1, t2 can each correspond to a duration between 2% and 30% of the duration of the entire injection phase, preferably between 10 and 20% of the duration of the entire injection phase.

Furthermore, it can be provided that the injection also takes place during partially overlapping time windows. In order to achieve the desired additional turbulence of the fuel spray when it is admitted into the combustion chamber of the cylinder, it is necessary for fuel not to be injected simultaneously with both injectors 10 during a time window within the opening phase of the inlet valves 9 .

Claims (9)

Method for supplying fuel to a combustion chamber of a cylinder (3) of an internal combustion engine (2), the cylinder (3) having an air-fuel mixture via at least two inlet sections (8), each connected to the cylinder via an inlet valve (9). (3) . ) is injected. procedure after claim 1 , wherein fuel is injected into the inlet sections (8) alternately. procedure after claim 2 , characterized in that, starting with a first of the injectors (10), fuel is injected for a first injection period (t1) and after the first injection period (t1) has elapsed, the injection of fuel through the first injector (10) ends and fuel is injected for a second period of time (t2) through a second one of the injectors (10). procedure after claim 3 , characterized in that after the second period of time (t2) has ended, injection is carried out again with the first injection valve (10). Procedure according to one of Claims 1 until 4 wherein fuel is injected into the inlet sections (8) by an injection valve (10) for an injection period (t1, t2) respectively, the injection period (t1, t2) having a duration comprised between 2% and 30% of the duration of the injection phase of the injectors (10). Procedure according to one of Claims 1 until 5 , characterized in that a first injection period (t1) of an injection through one injector (10) and a second injection period (t2) of an injection through the other injector (10) have the same injection period or different injection periods. Device for controlling a supply of fuel into a combustion chamber of a cylinder (3) of an internal combustion engine (2), the cylinder (3) receiving an air-fuel mixture via at least two inlet sections (8), each having an inlet valve (9). connected to the cylinder (3), with each of the inlet sections (8) being assigned an injection valve (10), characterized in that the device is designed to control the injection valves (10) in such a way that fuel enters the inlet sections ( 8) is injected asynchronously at least at times during an intake stroke of the internal combustion engine through the injectors (9, 10). Motor system (1) with an internal combustion engine (2) and with a device claim 7 . Computer program product containing program code which, when executed on a data processing unit, implements the method according to one of Claims 1 until 6 performs.

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